Historically, the literature on psychotherapy with borderline personality disorder has been based on object-relations theory or psychoanalytical approaches, rather than cognitive and behavioral approaches. In clinical assessment, the term borderline has been used to refer to patients with both neurotic and psychotic symptoms, a particular type of personality organization, or individuals who do not fit any other diagnostic category. To resolve the confusion, the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (1980) has established diagnostic criteria for borderline individuals which take into consideration the individual's long term functioning as well as periods of acute disturbance. Borderline personality disorder is characterized by limited basic assumptions, dichotomous thinking, and a weak sense of identity, all of which together form a mutually reinforcing and self-perpetuating system. Cognitive therapy with this population must be modified to allow for the difficulties borderline individuals have with relationships, goal setting, transference, and short term treatment. The therapist must strive for a calm, methodical approach, resisting the tendency to respond to each new crisis. Specific cognitive-behavioral techniques include establishing a trusting relationship, setting specific guidelines for behavior, and focusing on concrete behavioral goals. Behavioral experiments can be used to test limited assumptions and dichotomous thinking, while exploring advantages and disadvantages of various actions can aid impulsive behavior, power struggles, and fear of change. Identity building can be facilitated through feedback and identification of positive traits. Termination of therapy should always be a joint, well-reviewed decision. (BL)